The purpose of this study was to investigate the effects of tannin, which has antimicrobial and immunological properties, on hair growth in contact dermatitis induced by 2,4-dinitrochlorobenzene (DNCB). Mice (DNCB-DM) were exposed to dermatitis, and tannin aqueous solution (0.2W w / v% in 200 mL of tap water) was orally taken to dermatitis induced mice (DNCB-DM+T). The results were as follows: First, skin symptoms of mice in the DNCB-DM+T group treated for 3 weeks and 5 weeks showed dermatitis symptoms such as skin rash, papule, eczema and scab formation, but significantly reduced over the DNCB-DM group. There was no change in skin symptoms in the control group, O,A groups. Second, histological analysis of H & E staining showed clearly the boundary between the epidermal layer and the dermal layer, the border of the hair follicle, and the hair follicle cells in the DNCB-DM+T group than in the DNCB-DM group. Third, gene expression profiles of DNCB-DM+T group by analyzing transcripts of isolated total RNA were analyzed and mRNA levels of G protein-coupled receptor (Gprc5d), desmoglein 4 (Dsg4), keratin associated protein 4-16(Krtap4-16), patched 2 (Ptch2), homeobox C13 (Hoxc13), forkhead box Q1 (Foxq1), forkhead box N1 (Foxn1), and adenomatosis polyposis coli down-regulated1 (Apcdd1) were increased compared to the DNCB-DM group. In conclusion, tannin helps to improve symptoms of contact dermatitis, and changes in hair-related gene expression may help to improve the cycle or growth impediment of hair caused by dermatitis.